Filling demand which doesn't exist? China has an impoverished farmer/rural class to the tune of 600,000,000 - 700,000,000 people, and it is incredibly difficult to transition from a rural pass to a city pass, from what I've read. Difficulty in transition, to me, implies that their is a much greater demand to move into cities than the government is willing to allow currently. Why make it hard if you're begging people to move in?

EDIT: I know little of China, I'm posing this question in earnest to learn more!